School of Pure, Applied and Health Sciences

Influence of Elemental Composition of Geothermal Waters and Succulent Feedstocks on Cryo-mesophilic Biogas Production from Mt. Suswa, Kenya

2026-10-01T07:09:30Z

Influence of Elemental Composition of Geothermal Waters and Succulent Feedstocks on Cryo-mesophilic Biogas Production from Mt. Suswa, Kenya Evans Ochieng Odhiambo, Alloys Osano, Meshack Sitati Background: Dependence on charcoal and firewood in the Mt. Suswa region creates environmental and health concerns and supports the need to evaluate locally available feedstocks for renewable biogas production. This study investigated the elemental composition of geothermal waters and three succulent feedstocks and examined their biogas production under cryo-mesophilic conditions. Methods: Steam-vent water, water-pan samples, and Agave sisalana, Echinocactus grusonii, and Opuntia ficus-indica were analysed by Microwave Plasma Atomic Emission Spectroscopy. Biogas production was monitored for 132 h in 26 laboratory-scale batch digesters operated at 20–24.5°C with different feedstockwater combinations, with or without cow dung inoculum. Results: Agave sisalana contained 3,765.53 ± 0.00 g/L potassium, 1.23 ± 0.00 g/L cobalt, and 1.08 ± 0.03 g/L nickel. Region II steam-vent water had 50,268.93 ± 29.19 ppm potassium, 1,317.85 ± 1.10 ppm nickel, 1,184.54 ± 5.76 ppm cobalt, and the lowest measured arsenic concentration among the steam-vent regions The highest cumulative biogas yield was 62 mL in D6, containing A. sisalana, water-pan sample, and cow dung. Most O. ficus-indica treatments yielded 12–24 mL, although D10 reached 50 mL. Conclusion: Biogas performance varied with feedstock, water source, and inoculation. A. sisalana-based treatments and cow dung inoculation showed the most favourable overall performance under the tested conditions.

Exploring the Possibility of Using Agave sisalana Perrine, Austrocylindropuntia subulata (Muehlenpf) Backeb and Opuntia ficus- indica (L.) MILL. as a Source of Bio-electrolyte

2026-10-01T07:05:40Z

Exploring the Possibility of Using Agave sisalana Perrine, Austrocylindropuntia subulata (Muehlenpf) Backeb and Opuntia ficus- indica (L.) MILL. as a Source of Bio-electrolyte Mutindi Virginia, Aloys Osano, Oyaro Nathan The global search for sustainable and affordable green energy sources has intensified due to escalating environmental concerns, health issues, energy access challenges and fossil fuel depletion. Succulent plants such as Agave sisalana Perrine, Austrocylindropuntia subulata (Muehlenpf) Backeb and Opuntia ficus-indica (L.) Mill are fast-growing, drought-resistant and invasive in nature, thriving in arid and marginal lands where food crops cannot survive. These plants store significant amounts of water, bioinorganic and bio-organic matter, making them promising candidates for bio-electrolyte feedstock in renewable bio-fuel production. Currently, these plants do not have any significant use, yet they are invasive and are rapidly spreading, killing pasture for livestock in rural areas. This study investigated the potential of Agave sisalana Perrine, Austrocylindropuntia subulata (Muehlenpf) and Opuntia ficus-indica (L.) Mill saps as plant-based bioelectrolytes. Sap pH and electrical conductivity were measured at different temperatures and dilution levels, while voltage and current were measured using Zn-Cu, Zn-C, Zn-Fe, Fe-Cu, Fe-C and Cu-C electrode pairs. Pearson correlation and general linear model analyses were used to examine relationships among the measured variables. The results showed that pH and electrical conductivity decreased with an increase in temperature. Voltage showed relatively small changes during the short-term monitoring period but varied among plant species and electrode-pair combinations. Applied voltage had a weak positive correlation with current (r = 0.153, p < 0.001), while the Fe-Cu electrode pair recorded the highest estimated mean current of 3.66 mA. Overall, the results provided preliminary evidence that the three plant saps can function as bioelectrolytes in electrochemical cells.

On Unitary Quasi-Square Equivalence and Related Classes of Operators

2026-09-17T08:58:37Z

On Unitary Quasi-Square Equivalence and Related Classes of Operators Mwaura M Peter, John Matuya, Victor Wanjala This paper introduces and systematically investigates the notion of unitary quasi-square equivalence for bounded linear operators on Hilbert spaces. This equivalence relation, defined through the unitary equivalence of operator squares, provides a classification that preserves essential spectral and structural properties while capturing higher-order similarities not detectable through classical unitary equivalence. We establish that this relation defines a genuine equivalence relation and explore its connections with fundamental operator classes including square normal operators, n -quasi-normal operators, hyponormal operators, and various isometric structures. Our main contributions include complete characterization of spectral invariants preserved under this equivalence, demonstration of preservation theorems for advanced operator classes and their C * -algebraic structure, applications to concrete operator families, and development of decomposition theorems revealing the canonical structure of equivalence classes. The theory developed provides a tool for operator classification with applications to invariant subspace problems, similarity theory, and the structural analysis of non-normal operators.

On Deformed-Metric Equivalence of Hilbert Space Operators

2026-09-17T08:55:59Z

On Deformed-Metric Equivalence of Hilbert Space Operators Collins Amenya, Victor Wanjala, John Matuya This paper introduces and studies a novel class of equivalence relations in operator theory, called deformed-metrically equivalent operators. Two operators S and T in B(H) are said to be deformed-metrically equivalent if there exists a positive operator P such that S ∗PS = T ∗ T . This definition generalizes traditional metric equivalence by incorporating a positive deformation operator P, enabling a richer algebraic and spectral analysis. We establish several fundamental results, including the preservation of key operator classes such as normality, posinormality, and compactness under suitable commutativity conditions. Spectral inclusion relations are derived under invertibility assumptions, and the equivalence is shown to be stable under limits, tensor products, and functional calculus. Moreover, the set of all operators deformed-metrically equivalent to a given operator forms an affine space that is closed in the weak operator topology. These findings deepen the theoretical framework of operator equivalence and reveal new connections with well-studied classes such as posinormal, supraposinormal, and k-quasi n-power posinormal operators. T